A next-generation multimedia wireless communication system, which is being actively studied, is required to process various information such as images, wireless data, or the like, at a high data transmission rate, beyond the voice-oriented services provided at an early stage.
Thus, recently, orthogonal frequency division multiplexing (OFDM) exerting a high data rate receives much attention. The OFDM is a multi-carrier modulation scheme that divides a frequency band into a plurality of orthogonal subcarriers to transmit data. The OFDM can reduce an inter-symbol interference at a low complexity. The OFDM converts serially inputted data symbols into the N parallel data symbols, includes them in the N separated subcarriers, and transmits the same. The subcarriers maintain orthogonality in a frequency domain. The respective orthogonal channels experience mutually independent frequency selective fading, and the intervals of transmitted symbols is lengthened to minimize the inter-symbol interference. Orthogonal frequency division multiple access (OFDMA) refers to a multi-access scheme accomplishing multiple accesses by independently providing portions of available subcarriers to each user in a system using the OFDM as a modulation scheme. The OFDMA provides frequency resources called subcarriers to each user, and in general, the respective frequency resources are independently provided to multiple users so as not to overlap with each other. That is, frequency resources are mutually exclusively allocated to the users.
The wireless communication system has a cell structure to effectively configure a system. A cell refers to a zone obtained by dividing a wide area into smaller zones to effectively use frequency of cell. In general, a base station (BS) is installed at the center of the cell to relay a user equipment (UE). The cell refers to a service region provided by a single BS.
The wireless communication system uses a power control scheme to reduce a path loss according to the distance between a base station and a UE and an inter-cell interference by an adjacent cell. The power control scheme is adjusting transmission power to transmit data at the lowest power level while maintaining quality of service (QoS) of the wireless communication system. In particular, UEs located near a cell boundary in the multi-cell environment are much affected by the path loss and the inter-cell interference, so in transmitting data, the UEs should determine proper transmission power not to cause degradation of QoS by a path loss while not interfering with its adjacent cell.
The data transmitted by the UE to the BS may include user data and/or control information. A channel for transmitting the control information is called a control channel. The control information may include various types such as an ACK (Acknowledgement)/NACK (Negative-Acknowledgement) signal, a channel quality indicator (CQI), a precoding matrix indicator (PMI), a rank indicator (RI), or the like. The user data is transmitted as data, not control information, through a data channel. The control channel and the data channel may occupy different frequency domains or different time domains in the overall resource domain of the wireless communication system, so the control channel and the data channel may undergo different channel environments. If power control is performed without discriminating the control channel and the data channel, the efficiency of power control scheme may be lowered because of inaccurate determination of transmission power.
Thus, a method of transmitting data with accurate transmission power by discriminating the control channel and the data channel is required.